U.S. Pat. No. 3,528,420 discloses a coupling for ostomy appliances which takes the form of a pair of hard but nevertheless deformable plastic rings having generally frusto-conical sealing surfaces, one of the rings 20 being secured to a faceplate 16 and the other ring 14 being attached to ostomy bag 10. A lock flange 26 on the inner ring is intended to provide an abutment for the outer ring to lock or latch the rings together until separation is desired.
The latching system disclosed in that patent has not achieved notable commercial success and, although the reasons for such lack of success may be various, applicants have found that such an arrangement may be prone to unintentional detachment of the rings under conditions of use. Some deformability of the rings is necessary in order to permit intentional coupling and uncoupling; however, too much deformability may give rise to unintentional uncoupling of the rings in response to body movements of the wearer. The rings, especially faceplate ring 20, must therefore be relatively stiff, but such stiffness is also objectionable because body contact with a rigid ring may be expected to result in wearer discomfort.
One aspect of the present invention lies in the discovery that the system disclosed in the aforementioned patent may be the basis for a highly effective ostomy appliance coupling if the primary latching function is displaced radially outwardly and is performed by structure not indicated in that patent. With the essential function of the frusto-conical ring assembly of the patent limited to sealing rather than latching, and with the primary latching zone being located outwardly from the sealing zone, it has been found that the rings may be formed of a relatively soft plastic material (such as polyethylene) having substantial yieldability without risk that deformation might result in unintentional separation of the parts. The result is a ring assembly that has sufficient deformability for wearer comfort but still provides secure attachment and sealing effectiveness despite ring distortions arising from body movement. Intentional coupling and uncoupling may be readily achieved without direct contact with the stoma because the bag ring is disposed externally (radially outwardly) of the faceplate ring. Since the primary latching action occurs well outboard from the sealing zone, the result is a relatively flat ring assembly in which the radial width of each ring may be substantially greater than its axial depth.
In brief, the coupling ring construction of this invention takes the form of first and second coupling rings composed of flexible, resilient, thermoplastic material, the first ring having an annular body portion merging along its inner perimeter with a tubular neck portion that extends axially away from that body portion. The neck portion has a frusto-conical outer surface and has a free end terminating in an annular and radially-outwardly projecting rim.
The second ring also has an annular body portion and, in addition, an inner collar portion for detachably receiving the neck portion of the first ring. Unlike prior constructions, the annular body portions of both the first and second rings are generally planar with the body portion of the first ring having a latching shoulder extending about its outer perimeter and with the body portion of the second ring having an outer annular latching rib projecting inwardly and axially in a generally axial direction opposite from the direction of the collar portion. The latching rib, along with the remainder of the body portion of the second ring, defines an outer latching recess for detachably receiving and retaining the shoulder of the first ring.
The radial spacing between the latching and sealing functions promotes security of attachment even under severe conditions of use when the deformity of the rings is great enough to alter the areas of contact between the sealing surfaces. Under such circumstances, it has been found that since the parts continue to be held together by the primary latching action, normal sealing contact along the inner sealing zone is retained or restored when the deforming forces are removed.
Other features, advantages, and objects of the invention will become apparent from the specification and drawings.